"Block" or "Step" notch

[Diver1]

I was reading in Tim Ard, and Mike Bolin's book

The
Complete
Guide to
Chain Saw Safety
and
Directional Felling

http://www.forestapps.com/e-book/index.html

About the "Block" or "Step" notch and I was intriqued by some of the control posibilites that this notch offers. One thing the book did not mention was where the back cut should be made. It makes resonable sense to me that the back cut should be even with the top cut of the notch (see pic).

Has anyone here ever used this notch or know anything about it. How about some one on the West Coast the book says thats where this notch was developed?

Thanks

 

[Diver1]

Hey how do I post a pic?

 

[Diver1]

Hey I think I fiqured out the picture thing

 

[OutOnaLimb]

We covered a lot of different notch styles and benifits for each about a week ago. I was so busy that I joined the peanut gallery a few days to late and didnt want to fight with 5 pages of posts. Take a look at what was said in the thread about the felling cuts posted about a week ago.

RLTW
Kenn



:Monkey:

 

[tawilson]

I followed that thread and didn't see anything about a block notch. As a matter of fact, I just read it again to check.

 

[Stumper]

I have zero experience with a block notch as depicted. My experience with bending wood says that leaving a broader expanse of compression wood is going to give a longer control before failure. HOWEVER, when the back cut is a single kerf (and how else can we make them practically?) the forces still concentrate in the area immediately in front of the backcut. Some species will split a strip and create a long hinge strap to control the fall but most will simply break out the tension fibers from the backcut side and act very close to the same as a conventional notch. I typically broaden the back of my face cuts(notches) to create a longer(vertically) hinge strap. It adds a slightly longer control sweep before tearoff---sometimes) The only practical gain I can see(sitting here as an armchair expert on a technique I've never taken to the extreme illustrated) is that by slapping your backcut somewhere in the middle you are less likely to undercut or overcut the hinge.(both of which create some negative results).

 

[MasterBlaster]

Never seen that notch before.

 

[RescueMan]

Diver 1,

Is this what you mean by a block notch? And, if so, how the heck do you cut that?

- Robert

 

[RescueMan]

...and, Ted, would you recommend the e-book?

 

[Diver1]

RescueMan

The notch im interested in is as I have drawn it, and is used for felling. The one you have shown I believe is called a Tongue-and-Grove, and is used to keep logs from rolling after they have been bucked when cutting in steep terain.

I would very much recomend the e-book. It is packed with good information. It has the best technical information I have found for dealing with head, side, and back lean. I feel that it is as good as Douglas Dents book. Better in some areas. I baught the $29.95 printable version (I hate trying to read a book on the computer).

Thanks for all the coments, keep them coming. I would sure like to hear from someone who has used this notch.

 

[TheTreeSpyder]

i've only seen the block out face in huge tree pix such as Beranek's "The Fundamentals of General Treework" etc.; (kinda like an open dutchman?), sometimes in concunction with a humboldt ramp 1/2 way out from hinge(open step dutchman?).

i thought that Dent went with properly squaring the forces of a side lean into the face for balanced fall(square into face); while the Ard version went with oversteering the face to the side of intended fall to hit target by tree pulling to face and not quite making it? Which i thought of as not felling where the mechanichs placed (like Dent's) but rather targeting where the mechanichs would fail at directionally?

That is the way i read it when re-searching about getting the E-Book; but then it wouldn't let me order anyway at the time! But i might give it another try, if i could learn a few solids from it for that price.............

i would think that an open face gave more travel on hinge(?); but have no expereince with the block out face.

 

[ROLLACOSTA]

Originally posted by RescueMan
Diver 1,

Is this what you mean by a block notch? And, if so, how the heck do you cut that?

- Robert

are you sure your not trying to build a cabin???????

 

[Gord]

I have used a modified block notch for falling tops on dead cypress trees...the most tenacious holding fibers i see.
To me it seems that the notch offers more tearing leverage on the holding wood, a sharper jolt to snap the hinge.

 

[Kneejerk Bombas]

What's more important is what happens as it tipsover:

None of the fibers start to break until the face closes.

 

[Diver1]

As I see it the modified block closes before the tree reaches 90 degrees, where as with the block notch it closes at 90 degrees. If one was not careful and made the horizontal cuts to long it would act much like a kerf notch rater than a block notch. If this was the case it would close to soon and the tree would not have the momentum to tear the hinge.

From what Gord says it sounds like he comes very close to a block and the sudden rather than gradual closing of the notch tears the fibers.

What interests me about the block notch is that as I see it you would have longer hinge fibers. This would make them more flexible, also your notch would not close until you reached 90 degrees. These are control factors that under certain codintions could be very advantageous. If you desired to keep the spar attached to the stump and were concerned that the hinge fibers may be britle or prone to breakage, this would be a potential solution.

 

[TheTreeSpyder]

i think the short bottom ramp would make the snap off better that Gord refers to if the top of the ramp closed, became a pivot, as the bottom of ramp hadn't closed yet. Then, the weight past the pivot/top of ramp leverages against the fibers. This moving of the center pivot gives the fibers less leverage and the tree pulling more i think, for better pull/fiber tear.

i try to get this effect sometimes with more conventional notches than this block face strategy. Also, in air, to tilt a cut free block away from me, using the weght past the ramp/slide, to help pull the weight of the piece, with no fibers attatched though. But resistance is resistance wether weight or fiber; and making the first class lever with the top of ramp as pivot to aid in defeating the resistace can help IMLHO.

i think it can go like Mike pics, depending on the length and angle of ramp to height of cut relationship; or as i try to say.

 

[Diver1]

Spyder

I like your idea about the ramp and agree with you. I would not under most conditions use a block notch. With that said there have been times that I desired to keep the spar attacehed to the stume with the hinge, and I think that the block, or a modified block may do this better than other hinges.

What do you think?

 

[TheTreeSpyder]

Lots of variables, i think in general a wide face will give widest amount of travel possible, sometimes beyond needs. Though if done just right block could give as much travel as open face and friendlier pivot for support, with less load leverage and more support leverage.

i think of the block like an enlarged kerf face allowing more free movement. The block step as an enlarged buried kerf, 2 stage slap, or almost wide face, with more for support side than lod on the resulting pivot..

i think it is all mechanichs, small variables making lots of differances over ranges; so blanket statements hard.

i think it is leverages of how faces slap. If they hit on a point, that is the pivot, if the slap over a flat area, the center of the length from hinge is the pivot. That center pivot is a very dynamic choice, for moving it towards support hinge gives the tree more leverage and the hinge less at the same time; so the decision of placemeant has a compound effect. While if the pivot from faces slapping is moved away from hinge, the nhinge bgets more leverage, while the load of tree falling gets less.

If faces hit top of ramp, more leveraged force against a weaker leveraged hinge, for earlier tear, the later seating flat on the ramp to immedaiately change the mechanichs by moving the pivot to the center of that ramp; giving hinge more leverage and the load of felling forces less suddenly.

In Mike's drawing, the tree hits flatly so center of ramp would be pivot when faces closed, giving hinge more leverage and tree it tried to support less for hinge to fight. Perhaps this if placed right could give similar to or exceeding full face arc with less cutting(?); with as much/more allowable sweep, and support mechanichs changed by pivot deal.

Or something like that,
Good men.tall exercise in to understanding of theory and forces!
-:alien:

 

[John Paul Sanborn]

Originally posted by RescueMan


how the heck do you cut that?

- Robert

Plunge cut

 

[RescueMan]

Originally posted by John Paul Sanborn
Plunge cut

But...no conscientious chain saw operator ever cuts with the tip of their bar, right????????????????